Custo at end of last line of a score

[dpk]

For reasons of space I wish to print a chant which has two alternate endings by printing the common beginning once, followed by the two alternative endings on separate pages. At the end of this common opening, I’d like a custo to show the note the ending starts on (they both start on the same note).

I can of course use the + mark in my gabc score but that leaves a custo hanging in the middle of the line, which I find aesthetically unpleasing. What I'd ideally like is the custo to be pushed to the rightmost position on this final line, like all the other custos on the other lines are.

More generally, a way to do an \hfill to push parts of a score to the end of a line, regardless of the fact there’d be a gap in the middle, would be nice.

[davidweichiang]

This appears to work:

%%
g(g) g(g[gv:\hfill]) (h+)